Apple's Snow Leopard has been stalking us from the drifts for well over a year now. Little was seen of it while it circled for the first 12 months - picking its path, taking its time - but ever since Phil Schiller proudly showed off his new pet at WWDC, we've been waiting for it to pounce. The question is, now that it's here, launched in the UK for £25, is it something you really need to know about?

Those deep in the way of the Mac will already be fully versed on what this update to OS X is all about but if you're a new initiate to the cult or a lapsed believer we've put together a brief guide on all you need to know about version 10.6. Stick with Pocket-lint for a few minutes and we'll tell you what it's all about...

First up, if you hadn't gathered, Snow Leopard is simply the sexy name for the latest version of the Mac operating system. At the moment, most people will be using Leopard, which is Mac OS X version 10.5, and Snow Leopard is Mac OS X version 10.6. Also, the clue is in the name. Snow Leopard is really only an ostensibly subtle upgrade to the current version. Many of the improvements are under the hood with improvements in performance and efficiency rather large graphical changes to the front end user experience. So, don't be too disappointed if you buy and don't notice much difference at first.

Good question. So, long as your machine runs on an Intel CPU, you can. Snow Leopard sees Apple cut off their PowerPC machines which include the iBooks, Power Macs, PowerBooks, the G3-G5 iMacs, the G4 Mac Mini all the eMacs. We shouldn't imagine it's time to throw out your work horse just yet but it's probably a sign of things to come. If you're not sure which CPU your machine uses, look up the model on the Apple site orWikipedia and it'll tell you right there.

Once you've established that, you'll need 5GB of disk space on your machine and it'll have to have 1GB of RAM. Chances are that if your Mac has an Intel CPU, then it'll have a minimum of 2GB of RAM anyway but, again, worth checking. If disk space is a problem, then it's time for some virtual spring cleaning. Try emptying your wastebasket, deleting some unwanted images, burning some DVDs or even investing in some external storage.

The real advantage of Snow Leopard is that it heralds Apple's embrace of 64-bit computing. The majority of the applications on your machine will support the standard which allows for far quicker number crunching for the hardware you currently own and offers the same support into the future as you stuff more and more RAM inside your Mac. 64-bit applications also have more complex levels of security and, in theory, should render your machine less hackable - not that you're really too worried about that stuff if you own a Mac.

At the same time, Snow Leopard still fully supports any 32-bit apps you may have on your machine automatically but to, give you some idea, Apple's figures are that the 64-bit version ofQuickTime is 1.32x faster to launch and that the JavaScript in Safari is 1.5x quick too and that gives us a clue as to why Phil Schiller was raving about the browser's speed atWWDC . Safari 4 itself should also crash less. Its plug-ins will run separately and, according to the developers, it was those that caused most of the instabilities in the previous version.

The second important development in Snow Leopard is Grand Central Dispatch. Put crudely, it's a technology that organises and orchestrates the resources needed for all the applications to run. Each application needs to set up threads in any system in order to utilise more than one core of your computer's CPU. CPU cores are there to runsimultaneous tasks, so if your apps use threads, then it makes the machine run faster and smoother. Sadly not that many developers bother writing for threads because it's difficult and time consuming but whatGCD does is to take the threading process in-house and allow the Snow Leopard operating system to take care of it rather than the individual programs. Ultimately, that's going to be excellent but it will require developers to write forGCD for it to work. It should be easier than programming their own threads but might take a little while for everyone to start doing it.

The last piece of hardercore techhery worth knowing about is language called OpenCL. It takes the idea behind GCD one step further. If GCD gets the most out of your CPU, then what OpenCL does is allow your graphics processor to help out as well - for non-graphics based tasks as well that is. GPUs are incredibly powerful with huge numbers of cores and, with their help, Snow Leopard will get your Mac running even better.

To give you some perspective, your Mac will also wake up quicker, go to sleep quicker and join networks quicker. Finder will also be quicker running as a 64-bit application. You'll have quicker icon refreshes of JPEGs and PDF files as well as more options for your search. The installation of the new OS will be quicker than those of the past and take up 6GB less space on your HDD too. You Time Machine back up system will be quicker - working 50% faster than it did before - and your computer will be quicker to recognise connections and make fewer errors when ejecting discs.

QuickTime has been improved to QuickTime X featuring controls and a title bar that fades out of the panel when you're not using them, just as they have done in the past in Full Screen mode.Exposé and Stacks have also had a make-overs. Exposé will now work in the Dock for each application. If you click an hold on the icon it will shuffle and unshuffle all the windows for that particular application and it will display them in a grid for easier viewing. Stacks can now be scrolled though, as well, so you can keep as many files as you like in each folder and still be able to glance through them all.

Last of all, Snow Leopard will mean that your Mac now has out of the box support for Microsoft Exchange, so you can access your non-Mac work e-mail from your computer at home.

Well, that depends on what you're running at the moment and when you bought your Mac. Any Apple computer bought after 8th June 2009 is entitled to an upgrade for just $10. Good thing really as no one would be buying their computer in the interim otherwise.

If you're working on Leopard, then you can upgrade for $29 for a single machine or you can get a five-computer family pack for $49. Come to think of it, buying a family pack and then selling the other licenses on for a tenner each might work out quite nicely too but you didn't read that here.

Lastly, if you're still running Tiger (version 10.4) rather than the upgrade, you'll have to fork out for $169 the Mac Box Set which will include Snow Leopard, iLife '09, and iWork '09 for all your digital content organisation and office app needs.

That's your call really but it seems like you have to. Either you're using Leopard and $29 is very reasonable, or you're working on Tiger and it's quite a lot of money for what you're getting but then, if you're working on Tiger, then you're working on an OS that's over four years old. So, it's probably time to think about moving on anyway. Besdes, at least you'd be getting all the Leopard upgrades at the same time.